Lesnar by far. The size and strenght levels are just way too huge. Lesnar has superior wrestling and I doubt Cain can keep the match standing long enough. Besides, Lesnar proved his jaw is like indestructible in the match against Carwin and Carwin is a freaking powerful heavyhanded monster. Tbh. Only man in the UFC who can challenge Lesnar is Carwin, tho his cardio just sucks atm.